Rotary position sensors include potentiometers, resolvers, encoders and a variety of magnetic and capacitive technologies. Each device possesses characteristic advantages and disadvantages that make some devices more suitable for particular applications than others. A Non-contact Rotary Position Sensor, for example, converts rotary motion into an electrical signal to assist in providing the control data necessary for major chassis systems and other automotive and non-automotive applications.
The linear output voltage from a Non-contact Rotary Position Sensor's is directly proportional to the sensor's angle of rotation. Non-contact performance can be made possible by a variety of technologies that include the latest linear programmable, fully-integrated Hall Effect and Anisotropic magneto resistive (AMR) technologies.
The Hall Effect is based on an operating distance range, repeatability, various ranges from which to select, and a minimum target distance. The operating distance range is the absolute maximum range over which the device can provide sensible readings. Devices with various selectable ranges allow the device to be field-adjustable. Depending on the technology utilized, proximity sensors require a minimum target size.
Adding an integrated magnetic concentrator to a Hall Effect sensor enables high-accuracy 360° rotary position sensing. One example of a prior art 360° rotary sensor is disclosed in U.S. Pat. No. 6,707,293, entitled “360-Degree Rotary Position Sensor Having a Magnetoresistive Sensor an a Hall sensor,” which issued to Wan et al on Mar. 16, 2004 and is assigned to Honeywell International Inc. U.S. Pat. No. 6,707,293 is incorporated herein by reference. The Hall technology, based on integrated magnetic concentrators (IMCs), enables the development of small, cost-effective, high-accuracy noncontact rotary position sensors intended to solve long-standing challenges in 360° position sensing.
As automotive systems continue to develop in their complexity and performance, the increased need for rotary sensor products in the automotive market demands an improved robust design. Eccentricity or dislocation of the magnet position may occur due to harsh operating conditions such as, for example, wear and tear in the lifecycle, which is most common in automotive applications.
One prior art sensing technique involves the use of a diametrically magnetized solid magnet that drives a parallel field magnetic sensor based on Hall or AMR technology. Such a technique and/or apparatus contain several limiting constraints. Based on the stimulation results, for eccentricities of +/−0.46 mm on X and Y axes, which is common in automotive applications, the Bx and By output varies by 1.96% & 0.68% respectively. Due to this issue, achieving the same repeatability every time when the sensor is tested is questionable.
Because of the increase in error, the correlation error in dual o/p sensor may be increased. Based on the stimulation results, a tilt of the magnet for +/−3 degrees on the X axis can cause the Bx and By parameters to vary by 4.89% & 4.7% respectively. A tilt of 3 degrees can be due to the clearance between the rotating parts. The clearance can be provided to enable free rotation of the parts.
Due to an increase in the B field components error, the linearity and correlation errors, in the case of dual o/p sensors, can increase. Polarity identification during the assembly of the sensor calls for a tedious process that increases product costs. The centrality between the magnet and the sensor IC must be maintained in an ideal location, which is critical to effective sensor operations. A mechanical support can be, for example, actually provided by a bonding at the bottom or a potting located at the top side of the magnet. There is no pole to hold the magnet inside the rotor slot.
Based on the foregoing, it is believed that a need exists for a robust design to overcome the problems of eccentricity or dislocation of the magnet position with respect to the desired position with sensing element. It is believed that the system and method disclosed herein provides a solution to these problems by offering a configuration in which a hollow cylindrical magnet design can be implemented to drive the parallel field magnetic sensor with a unique configuration based on Hall/AMR technologies.